Patent Document 1 discloses a device in which a breakout punch (knockout pin) is operated by means of a cam. In the device, a rotational force from a crankshaft is transmitted to the cam so as to rotate the cam synchronously with the crankshaft and to operate the breakup punch. Since the device is interlocked with the press crankshaft, the knockout punch cannot be operated with single.
Further, Patent Document 2 discloses a knockout device characterized in that a Whitworth mechanism is used. In the knockout device, output force of a servo motor is increased by means of the Whitworth mechanism to generate a large torque at knockout operation.
Hitherto, there has been a transfer device, which transfers a work between dies of a transfer press machine or tandem press line. As shown in FIG. 13, the transfer device repeats a series of motions of clamping the work by left and right feed-bars, lifting-up, advancing forward, bringing down, releasing (un-clamping) the work to set on next press position, and return the feed-bars to the original position again.